It is well known that traditional surgical procedures in locations deep within a patient's body require a long incision, extensive muscle stripping, prolonged retraction of muscles for visualization, and denervation and devascularization of the adjacent tissue. These procedures result in extensive tissue traumatization and consequently in prolonged recovery time, risk of infections, high hospitalization costs, pain that can be more severe than the pain due to the initial ailment, and in some cases permanent scarring. In minimally invasive surgical procedures, portals are used to access the locations deep in the patient's body. The use of portals rather than a long incision causes less trauma to the adjacent tissue, reduces the recovery time and pain and may be performed in some case under only local anesthesia. The avoidance of general anesthesia reduces post-operative recovery time and the risk of complications.
Minimally invasive surgical procedures are especially desirable for spine surgeries because spine pathologies are located deep within the body without clear muscle planes and there is danger of damaging the adjacent neural and vascular tissues. In treating the majority of spinal pathologies, the spinal muscles are stripped from the bony elements of the spine followed by laminectomy to expose the dura, the nerve roots, and the discs. The incision has to be wide enough and the tissues have to be retracted to maintain a channel from the skin to the floor of the spinal canal that will allow direct visualization. The destruction to the spinal structures is even more extensive during fusion procedures, which require more lateral tissue dissection and exposure to access the transverse processes and pedicles for placement of pedicle screws, rod constructs for stability, and bone graft under direct vision.
Multiple attempts have been made to improve the techniques, devices, and instrumentations used for minimal and percutaneous surgery. These include use of percutaneous needle administration of chemonucleolytic agents to enzymatically dissolve the disc and the use of microscopes and loupe magnification to limit the incision size. These two approaches are at the foundation of minimal access surgery, one using an injectable agent and the other using a device to limit the exposure while maximizing the visualization. Unfortunately, the effectiveness and safety of the enzyme, chymopapain used for chemonucleolysis, have been complicated by severe spasms, post-operative pain, and sensitivity reactions including anaphylactic shock. Loupe magnification and microscopes are helpful for improving visualization but are not effective without retractor systems and specialized instruments and devices to make minimal access surgery effective.
Substantial progress has been made to develop the necessary devices, instruments, and methods to effectively improve minimal access surgery resulting in improved visualization, less tissue injury, less general anesthesia exposure and improved recovery time and post-operative pain. For example U.S. Pat. Nos. 5,792,044 and 5,902,231 by Foley et al., demonstrate some of the improved methods and instruments for percutaneous surgeries.
A problem that occurs frequently in minimally invasive surgical procedures is related to the fact that it is not always known how deep the pathology is located. Accordingly there is a need for a portal with a variable length to accommodate the locations of the various pathologies. Furthermore, in spine fusion procedures intervertebral spacers or connecting elements, such as rods, plates or wires are placed and fixed between two or more locations of the spine. Placement of these spacers or connecting elements requires open surgery, which is currently one of the major limitations of other percutaneous cannula access methodologies. Accordingly there is a need for improved methods, tools and devices that provide percutaneous access in minimally invasive spinal surgeries.